Use nginx for file downloads instead of apache

A website that grows rapidly is based on Apache web server. It serves large files to a large number of users. All downloads are handled by php-fastCGI which controls the download speed. The number of open connections soon adds up and Apache uses alot of resources to serve a relatively small number of concurrent downloads. In order to free apache and php from this job and allow alot more simultaneous downloads, I need you to configure the requests to be forced thru nginx. Nginx is installed and running on the system, it is configured with correct permissions, can be accessed thru a subdomain and has access to the files. The website is in PHP, it uses MySQL.